Thirty Meter Telescope Warping Harness Control System

Sensing and Control Systems

Accurate, automated aberration compensation

The Thirty Meter Telescope (TMT) team asked S[&]T to build a test control unit for the warping harness, which will compensate for optical aberrations to the TMT's 492 mirror segments. The TMT's thirty meter namesake mirror can be tilted towards the sky at various angles, and with each angle there are varying gravity effects on the mirror. To correct for these deformations, a warping harness situated underneath the mirror will be actuated by a control system developed by S[&]T. This control system allows scientists to compensate for known aberrations with nanometer precision. The warping harness will be remotely controlled, and re-adjusted periodically (not continuously), allowing automated corrections of quasi-static and temperature-induced effects, up to 10 times per night.

How it works

S[&]T developed a Test Control Unit (TCU) for actuation of 21 stepper motors attached to leafsprings connected to whiffletree structures supporting each of the 492 mirror segments of the TMT. The system includes signal conditioners that use strain gauges mounted on the leafsprings to monitor torque applied to the system via the stepper motors. Two sorts of control software were developed to support intelligent testing of the warping harness. A graphical user interface helps test engineers monitor and control system status in a clear overview. S[&]T also provided a python scripting environment in which test engineers can easily develop custom scripts for automated testing.

Project Support

S[&]T provided support to the demonstration and acceptance testing on location at TMT headquarters in Los Angeles, California. We provided training to help test engineers get acquainted with our TCU control software and system. The control systems team also developed custom scripts for accelerated lifetime tests, and provided support to the profilometer test at Coherent in San Francisco.

Project Status

S[&]T successfully delivered the TCU for TMT's engineering model of a mirror segment, including the essential warping harness structure. We hope that we are able to provide more testing and control support as TMT moves further toward fruition, and that our control units become a core part of ensuring a working warping harness concept.